Ballast circuit for gaseous discharge lamps

ABSTRACT

A ballast circuit for a fluorescent bulb comprises a voltage quadrupler circuit in series with a ballast resistor and the bulb. The quadrupler circuit comprises a voltage doubler circuit whose output voltage is doubled by a second voltage doubler circuit. The first voltage doubler circuit includes a first pair of series capacitors capable of supplying lamp current at operating voltage. The second voltage doubler circuit comprises a pair of series capacitors for providing full quadrupler voltage for no-load triggering but negligible effect under load and have a capacitance that is much smaller than the capacitance of the first doubler capacitors. A variable resistance in series with the first voltage doubler circuit may function as a dimmer control.

Tenen 1 1 Sept. 30, 1975 15 1 BALLAST CIRCUIT FOR GASEOUS 3.713.018 1/1973 Tschcuschncr 321 15 DISCHARGE LAMPS Milford. NH. 03055 fcohcn l [22] Filed: Dec. 26, 1973 12.11 App]. No: 428,025 ABSTRACT A ballast circuit for a fluorescent bulb comprises a f) voltage quadrupler circuit in series with a ballast resis- [32] 11.8. Cl..... 315/200 R; 3l5/Dl(1. 4; 315/30 R1 tor and the bulb. The quadrupler circuit comprises a 3l5/-4l R voltage doubler circuit whose output voltage is dou- {51] 1111i. Cl. H05B737/00 b by A Second voltage doubler Circuit. The first [58] Flew of Search 3 "g voltage doubler circuit includes a first pair of series 3 l/-4l 3-1/1? capacitors capable of supplying lamp current at operating voltage. The second voltage doubler circuit coml56] References ("med prises a pair of series capacitors for providing full UNITED STATES PA ENT quatlrupler voltage for no-loatl triggering but negligi 2.056.376 10/1936 Travis 321/ blc effect under load and have a capacitance that is 2.301.891 11/1942 Lecorquillier 315/127 much smaller than the capacitance of the first doubler 3.155.8 5 11/ a h Ct 111- 5/305 X capacitors. A variable resistance in series with the first 3375933 9/1966 Y CI 331/1 5 voltage doubler circuit may function as a dimmer con 3.493.840 2/1970 Rosenberg... 321/15 trol- 3.6-l6.425 2/1972 Beck etal.... 121/15 3.710.184 1/1973 Williams 315/227 6 Claims, 1 Drawing Figure (33 465:2,iow BALLAST 34 FIUELRESCENT 36 B CAPACITIVE 27 SYLVANIA TRIGGER .ooa2,4oov WW 22 a CIRCUIT BREAKER m'zsw DIMMER BALLAST CIRCUIT FOR GASEOUS DISCHARGE LAMPS BACKGROUND OF THE INVENTION The present invention relates in general to ballast circuits for fluorescent lights and more particularly concerns novel apparatus and techniques for initially igniting a fluorescent or other gaseous discharge lamp and efficiently sustaining ignition with a compact quiet ecol nomical lightweight circuit that provides the additional feature of facilitating economical intensity control over a continuous range of intensities.

It is an important object of this invention to provide an improved ballast and starter circuit for gaseous discharge lamp, such as a fluorescent bulb.

It is a further object of the invention to achievethe preceding object while providing especially convenient means for controlling lamp intensity. I

It is a further object of the invention to achieve one or more of the preceding objects with a circuit comprising low-cost electronic components.

It is still a further object of the invention to achieve one or more of the preceding objects with a circuit capable of energizing a number of fluorescent lamps in parallel.

It is another object of the invention to achieve one or more of the preceding objects with compact economical apparatus that is relatively easy and inexpensive to fabricate by relatively inexperienced personnel and functions reliably for relatively long intervals. U

SUMMARY OF THE INVENTION According to the invention, there is a first voltage doubler circuit in series with an a-c power source. The first voltage doubler circuit includes means for substantially doubling the voltage across an input terminal pair and comprises first and second unilaterally conducting devices connected in series and shunted by first and second capacitors connected in series to form a bridge circuit means for receiving a-c energy applied between the junction of the unilaterally conducting devices and the junction of the first and second capacitors. Third and fourth unilaterally conducting devices are connected in series between respective ones of the junctions between unilaterally conductive devices and capacitors in the bridge circuit means and a gas discharge lamp. Third and fourth capacitors are connected in series across the series combination of the four unilaterally conducting devices. The junction of the third and fourth capacitors is connected to the junction of the first and second unilaterally conducting devices.

A ballast resistor is connected in series between the four unilaterally conducting devices and the gas discharge lamp. An optional capacitive trigger electrode adjacent to the bulb is connected to the junction of the ballast resistor and a terminal of the lamp. In a preferred form of the invention a variable resistance is connected in series between the bridge circuit means and the input terminals for controlling the current to and brightness of the lamp.

Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing,

BRIEF DESCRIPTION OF THE DRAWING the single FIGURE of which is a schematic circuit diagram of an exemplary embodiment of the invention.

.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawing, there is shown a schematic circuit diagram of an exemplary embodi' ment of the invention in which power from conventional a-c plug 11 ignites and illuminates fluorescent bulb 12 when switch arm 13 is moved to the high or low positions. While the specific embodiment includes a fluorescent bulb, the principles of the invention are applicable to other gas discharge lamps, such as an HeNe gas laser tube.

The circuit comprises voltage doubler diodes l4 and 15 shunted by voltage doubler capacitors l6 and 17. The junction of capacitors I6 and 17 is connected to terminal 21 of a-c plug 11 through switch arm 13 and through dimmer resistance 18 in the low position as shown and directly when in the high position. The junction between diodes l4 and 15 is connected to the other terminal 22 of a-c plug 11 through circuit breaker Trigger diodes 23 and 24 are connected to junctions 25 and 26, respectively, of the voltage doubler bridge circuit comprising diodes l4 and 15 and capacitors l6 and 17. Trigger capacitors 27 and 28 are connected in series across the four diodes 14, 15, 23 and 24 between +junction 31 and -junction 32. The junction of capacitors 27 and 25 is connected to terminal 22 of a-c plug 11 and the junction of diodes l4 and 15.

A ballast resistor 33 is connected between positive junction 31 and electrode 34 of fluorescent lamp 12. The other electrode 35 of fluorescent lamp I2 is connected to negative junction 32. A capacitive trigger electrode 36 adjacent fluorescent lamp I2 is also connected to electrode 34. Representative parameter values are set forth on the diagram.

Having described the physical arrangement of circuit components, the mode of operation will now be described. It is convenient to initially assume that switch arm 13 is in the off position with lamp 12 then extinguished and presenting a relatively high impedance between junctions 31 and 32. When switch arm 13 is moved to either the high or low positions, very shortly thereafter substantially four times the peak potential between terminals 21 and 22 appears between terminals 31 and 32, and, hence, between capacitive trigger electrode 36 and lamp electrode 35 to thereby ignite lamp 12. When lamp l2 ignites, its impedance drops, the current through it increases and the voltage between electrodes 34 and 35 drops because most of the current then flows through capaciitors 16 and 17 of much lower impedance than trigger capacitors 27. and 28 so that the voltage increasing effect of the trigger capacitors is then negligible. The current through fluorescent bulb l2 is then limited by ballast resistor 33 and dimmer resistor 18 with switch arm 13 in the low position asindicated.

While in the specific example shown, dimming is indicated as being effected by switching in a fixed resistor, it is within the principles of the invention to use a variable resistance to provide a continuous range of light intensity. It is also within the principles of the invention to have the variable resistance comprise a photocell characterized by a resistance that is inversely proportional to light intensity so that the brightness of lamp 12 would track the ambient light level. That is to say, as the ambient light level increased, the intensity of lamp 12 would increase.

It is evident that various components may be interchanged. For example, ballast resistor 33 could be in the lead between junction 32 and electrode 35. The switch and dimmer assembly could be connected in the lead from terminal 22.

It is also within the principles of the invention to use higher voltage multiplying coefficients, for example six and eight which would be required for use with an HeNe gas laser tube, for example.

It is evident that those skilled in the art may now make numerous other modifications and uses of and departures from the specific embodiments described herein without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of featurespresent in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims.

What is claimedis:

1. A gas discharge lamp starting and ballast circuit comprising,

an input terminal pair for receiving a-c energy,

first voltage doubler circuit means coupled to said input terminal pair for substantially doublingthe peak voltage between said input terminal pair and comprising first and second unilaterally conductive devices connected in series and poled in the same sense shunted by first and second capacitors connected in series to form a bridge circuit having four junctions with the junction between said first and second unilaterally conductive devices coupled to one terminal of said input terminal pair and the junction between said first and second capacitors coupled to the other terminal of said input terminal pair,

second voltage doubler circuit means for selectively substantially doubling the voltage provided by said first voltage doubler circuit means and comprising third and fourth unilaterally conducting devices separated by, connected in series with and poled in the same sense as said first and second unilaterally conducting devices and third and fourth capacitors connected in series across the series combination of said first, second,.third and fourth unilaterally conducting devices with the junction of said third and fourth capacitors coupled to the junction between said first and second unilaterally conducting devices,

the impedance of said first and second capacitors being much lower than the impedance of said third and fourth capacitors whereby the current flowing through said first and second capacitors when a gas discharge lamp is connected in series between the junction of said third capacitor with said third unilaterally conducting device and the junction between said fourth capacitor with said fourth unilaterally conducting device is so much greater than the current then flowing through said third and fourth capacitors that the voltage increasing effect of saidthird and fourth capacitorsis then negligible,

whereby said first voltage doubler circuit means, said second voltage doubler circuit means and said gas discharge lamp may comprise means for initially.

establishing both said voltage doubler circuit ducting device and the junction of said fourth capacitor with said fourth unilaterally conducting device.

3. A gas discharge lamp starting and ballasting circuit in accordance with claim 1 and further comprising,

variable resistance means connected in series between said input terminal pair and said first voltage doubler circuit means for controlling the current delivered by saidvoltage doubler circuit meansto control the intensity of a lamp attached thereto. 4. A gas discharge lamp starting and ballast circuit in accordance with claim 1 and further'comprising,

said gas discharge lamp direct coupled between the junction of said third unilaterally conducting device withsaid third capacitor and the junction of said fourth unilaterally conducting device with said fourth capacitor, and variable impedance means coupled between said input terminal pair and said first voltage doubler circuit means for selectively controlling the brightness of said lamp.

5. A gas discharge lamp starting and ballastcircuit in accordance with claim 1 and further comprising,

said gas discharge lamp direct coupled between the junction of said third unilaterally conducting device with said third capacitor and the junction of said fourth unilaterally conducting device with said fourth capacitor, trigger electrode means capacitively coupled to said gas discharge lamp and direct coupled to the junction of said third unilaterally conducting device with said third capacitor for initially coupling said output voltage more than twice the peak voltage to said lamp for igniting said lamp. 6. A gas discharge lamp starting and ballast circuit in accordance with claim 5 and further comprising ballast impedancemeans connected between the junction of said thirdunilaterally conducting device with said third capacitor and said gas discharge lamp for limiting the current through said lamp when said lamp is conducting. 

1. A gas discharge lamp starting and ballast circuit comprising, an input terminal pair for receiving a-c energy, first voltage doubler circuit means coupled to said input terminal pair for substantially doubling the peak voltage between said input terminal pair and comprising first and second unilaterally conductive devices connected in series and poled in the same sense shunted by first and second capacitors connected in series to form a bridge circuit having four junctions with the junction between said first and second unilaterally conductive devices coupled to one terminal of said input terminal pair and the junction between said first and second capacitors coupled to the other terminal of said input terminal pair, second voltage doubler circuit means for selectively substantially doubling the voltage provided by said first voltage doubler circuit means and comprising third and fourth unilaterally conducting devices separated by, connected in series with and poled in the same sense as said first and second unilaterally conducting devices and third and fourth capacitors connected in series across the series combination of said first, second, third and fourth unilaterally conducting devices with the junction of said third and fourth capacitors coupled to the junction between said first and second unilaterally conducting devices, the impedance of said first and second capacitors being much lower than the impedance of said third and fourth capacitors whereby the current flowing through said first and second capacitors when a gas discharge lamp is connected in series between the junction of said third capacitor with said third unilaterally conducting device and the junction between said fourth capacitor with said fourth unilaterally conducting device is so much greater than the current then flowing through said third and fourth capacitors that the voltage increasing effect of said third and fourth capacitors is then negligible, whereby said first voltage doubler circuit means, said second voltage doubler circuit means and said gas discharge lamp may comprise means for initially establishing both said voltage doubler circuit means operative for providing an output voltage more than twice the peak voltage between said first and second voltage doulber circuit means from said input terminal pair and thereafter rendering only said first voltage doubler circuit means operative for providing at the output of said first and second voltage doubler circuit means a voltage substantially twice that between said input terminal pair.
 2. A gas discharge lamp starting and ballasting circuit in accordance with claim 1 and further comprising said gas discharge lamp direct coupled between the junction of said third capacitor with said third unilaterally conducting device and the junction of said fourth capacitor with said fourth unilaterally conducting device.
 3. A gas discharge lamp starting and ballasting circuit in accordance with claim 1 and further comprising, variable resistance meaNs connected in series between said input terminal pair and said first voltage doubler circuit means for controlling the current delivered by said voltage doubler circuit means to control the intensity of a lamp attached thereto.
 4. A gas discharge lamp starting and ballast circuit in accordance with claim 1 and further comprising, said gas discharge lamp direct coupled between the junction of said third unilaterally conducting device with said third capacitor and the junction of said fourth unilaterally conducting device with said fourth capacitor, and variable impedance means coupled between said input terminal pair and said first voltage doubler circuit means for selectively controlling the brightness of said lamp.
 5. A gas discharge lamp starting and ballast circuit in accordance with claim 1 and further comprising, said gas discharge lamp direct coupled between the junction of said third unilaterally conducting device with said third capacitor and the junction of said fourth unilaterally conducting device with said fourth capacitor, trigger electrode means capacitively coupled to said gas discharge lamp and direct coupled to the junction of said third unilaterally conducting device with said third capacitor for initially coupling said output voltage more than twice the peak voltage to said lamp for igniting said lamp.
 6. A gas discharge lamp starting and ballast circuit in accordance with claim 5 and further comprising ballast impedance means connected between the junction of said third unilaterally conducting device with said third capacitor and said gas discharge lamp for limiting the current through said lamp when said lamp is conducting. 